Aetna CEO: Obamacare In A 'Death Spiral' Heading Into 2018. Aetna and Humana have called off their deal amid government concerns over competition. Here's a look back at six pivotal moments that led to this. Aetna and Humana have called off their deal amid government concerns over competition.
For the plant genus, see Synapsis (plant). Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis.
Synapses on somas are termed axosomatic synapses; those on dendrites are termed axodendritic; and those on other axons or boutons are axoaxonic. The fiber's bouton is called the presynaptic element and the structure it contacts is the postsynaptic element. A schematic diagram of a synapse is shown in Figure 13-1A. The pre- and postsynaptic elements are separated by a space 15-200 nm wide, known as the synaptic cleft.